{"title":"Relationships between Stratospheric Quasi-Biennial Oscillation (QBO) and Precipitation Activities in Asia","authors":"M. Inoue, S. Yamakawa","doi":"10.5026/JGEOGRAPHY.119.441","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.119.441","url":null,"abstract":"The influence of stratospheric quasi-biennial oscillation (QBO) on global precipitation features was studied over a 25-year period. The years from 1980 to 2004 are classified into easterly and westerly phases of QBO. Composite analyses in Asia reveal noteworthy pluvial anomalies near the Philippines, and inactive front activity and typical drought events due to adiabatic descent over Japan during the easterly phase of QBO. Cool summers and extreme rainfall events in Japan tend to prevail in the westerly phase. In particular, ten Typhoons struck Japan in 2004 accompanied by the westerly phase of QBO.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122795297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"日本最古の堆積岩年代472Ma（オルドビス紀前期末）とその意義","authors":"隆晃 中間, 岳史 平田, 茂 大藤, 茂徳 丸山","doi":"10.5026/JGEOGRAPHY.119.270","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.119.270","url":null,"abstract":"The Hitoegane Formation, with the Middle Ordovician conodont, in the Hida marginal belt, Southwest Japan, represents the oldest sedimentary unit in Japan. In order to date the lowest part of the formation, U-Pb age of igneous zircon from tuff beds was measured by LA-ICP-MS. A felsic tuff bed from the lower part of the Hitoegane Fm was newly dated 472 Ma (latest Early Ordovician) that marks the oldest age for sedimentary unit hitherto reported from Japan. This result suggests that the basement of proto-Japan was probably older than the Ordovician. The Iwatsubodani Formation, an apparently underlying unit below the Hitoegane Fm, however, yielded U-Pb zircon age of 280 Ma (Early Permian). Thus this unit is too young to be the sedimentary basement of the Hitoegane Fm. Newly added also were some pieces of information on the U-Pb ages and stratigraphy of the Paleozoic-Mesozoic sedimentary units of the Hida marginal belt.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"178 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124421863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"西南日本における海溝–島弧–縁海系の地殻構造","authors":"谷生 伊藤, 佐藤 比呂志","doi":"10.5026/JGEOGRAPHY.119.235","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.119.235","url":null,"abstract":"The first attempt to make a crustal-scale cross-section of a trench-arc-backarc sea system has been successfully accomplished from the Nankai trough to the northern margin of the Yamato basin across Southwest Japan, using three seismic profiles: Nankai trough to Japan Sea coast (Ito et al., 2009), Oki trough (Tanaka and Ogusa, 1981), and Yamato basin (Sato et al., 2006). The section contains much new information that will be useful for research on the structural development of the Japanese island arc. The highlight of the information is the substantial difference in the structure between the Outer and the Inner zones. The Outer zone is constructed mainly by N-dipping accretionary complexes in its upper crust with a poorly developed lower crust. On the contrary, the Inner zone exhibits predominantly horizontal structures in its upper crust, beneath which thick horizontal lower crustal laminations occur as in the continental lower crust. Furthermore a 10-km-thick lens-shaped olivine-pyroxene cumulate body underlies the lower crust. The N-dipping Median Tectonic Line juxtaposes two substantially different zones from the upper to lower crusts The section, however, has the following serious defects caused by the poor specifications of the seismic profilings used here: (1) Shallow structures (<about several km) are poorly imaged, which makes it difficult to interpret geological structures. (2) Seismic images beneath the on-and-offshore zones of the Japan Sea coast are missing, which also makes it difficult to understand the rifting process associated with the opening of the Japan Sea. Thus, a new crustal-scale cross-section that is free from these defects is necessary. Fortunately, both the theory and the techniques of seismic profiling have advanced tremendously recently. This situation enables us to conduct seismic profiling along a long seismic line simultaneously on both land and sea (so-called “integrated land-and-sea seismic profiling”), and to provide a new section. The new section is expected to replace the former one soon.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133379989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Variations of Solar Activity and Climate during the Past 1200 Years","authors":"H. Miyahara","doi":"10.5026/jgeography.119.510","DOIUrl":"https://doi.org/10.5026/jgeography.119.510","url":null,"abstract":"The relationship between solar activity and climate change in the past can be examined using proxy records. Variations of solar activity can be reconstructed based on carbon-14 in tree rings, which are produced by galactic cosmic rays modulated by the solar wind, while climate change can be reconstructed from changes of tree-ring growth rate or content of stable isotopes in ice cores from the polar region. A comparison of solar activity and climate change at the Maunder Minimum in the 17th century and the Early Medieval Maximum Period in the 9-10th century suggests that the sun plays an important role in climate change even on a decadal time scale. The characteristic variations detected in climate change suggest the mechanism of solar influence on climate involves galactic cosmic rays. Variable features of eleven-year and twenty-two year cycles of solar activity and consequent variations of cosmic rays are possible origins of complex variations of climate change on decadal to multi-decadal time scales. We summarize variations of solar activity and cosmic rays during the past 1200 years and their possible influence on climate change.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116759812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"フィッション・トラック熱年代に基づいた六甲地域の冷却・削剥史","authors":"茂 末岡, 高広 田上, 浩之 堤, 徳子 長谷部, 明弘 田村, 章司 荒井, 隆二 山田, 達生 松田, 小村 健太朗","doi":"10.5026/JGEOGRAPHY.119.84","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.119.84","url":null,"abstract":"Quantitatively estimating denudation is generally difficult because it essentially involves the removal and loss of materials in situ. The denudation rate of mountainous areas in Japan has commonly been studied from the volume of sediment in a basin or catchment. Nonetheless, the availability of these methods is constrained spatially by upstream area and temporally by depositional age. In the last few decades, thermochronometric methods that evaluate thermal history using radiometric-dating methods have been used to evaluate the denudation and tectonic history of orogenic belts around the world. The advantages of thermochronometric methods are that we can calculate the denudation rate at each sampling point and that combining multiple methods and/or target minerals enables us to calculate denudation rates in multiple periods. However, thermochronometric methods have been applied to areas with extraordinarily high denudation rates in island arc areas such as Japan. Thus, the effectiveness of thermochronometric methods for estimating denudation rates in island arc areas has not been demonstrated. We applied apatite and zircon fission-track thermochronometry to granitic rock samples collected from outcrops and a borehole to estimate the tectonic history of the Rokko area, southwest Japan. Previous studies suggested that the Rokko Mountains have been uplifted by active faulting along their northern and southern margins during the Rokko movements, a Quaternary tectonic movement in the Kinki district. However, the tectonic history of the Rokko area prior to 1 Ma has not been revealed due to a lack of prevalent geologic markers. We estimated average denudation rates in various periods based on apatite and zircon FT ages and previously reported radiometric ages. We obtained denudation rates at about 0.04-0.10 mm/yr after about 30 Ma, 0.05-0.7 mm/yr during 50-30 Ma, 0.7-4.0 mm/yr during 70-50 Ma. The denudation rate after the deposition of the Kobe Group (36.9-30.4 Ma) is estimated to be in the 0.01-0.1 mm/yr order, while bedrock uplift rate after about 1 Ma is estimated to be about 0.5 mm/yr. Thus, the tectonic activity of the Rokko Mountains area prior to 1 Ma has been relatively low.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134218127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Estimation of History of Hydrothermal Activities Based on Evolutionary Ecology of Chemosynthesis-based Communities","authors":"S. Kojima, H. Watanabe, K. Fujikura","doi":"10.5026/jgeography.118.1174","DOIUrl":"https://doi.org/10.5026/jgeography.118.1174","url":null,"abstract":"In deep-sea reducing environments, such as hydrothermal vent fields and cold seep areas, biological communities with huge biomass are often observed. Such communities associated with bacterial chemosynthesis, which are composed of species endemic to these environments, are founded with hydrothermal activities and succeed with changes of activities. Over a longer timescale, genetic deviations among local populations and speciation occur during the course of a series of activities and finally new faunal groups diverged. We attempt to estimate the ages of various hydrothermal phenomena on various timescales from 10 to 107 years on the basis of the evolutionary ecology of animals endemic to hydrothermal vents as part of the “Taiga project”. In this paper, we introduce communities in hydrothermal vent fields and describe the principals of methodologies for age estimation, which we are now planning, and the expected results.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133648698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Review of Oceanic Crustal Structure and Seafloor Hydrothermal Circulation","authors":"Y. Kawada, N. Seama, K. Okino","doi":"10.5026/JGEOGRAPHY.118.1037","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.1037","url":null,"abstract":"Seafloor hydrothermal systems are important in relation to global heat and chemical fluxes as well as the distribution of microbial communities within the oceanic crust. From a global context, low-temperature hydrothermal systems located far from the ridge axes are of great importance, because of their large covered area. Our current understandings of seafloor hydrothermal systems come mainly from high-temperature systems on fast-spreading ridges, which are assumed to be typical. Recently, observations have been conducted on high-temperature systems at slow- and ultraslow-spreading ridges. In addition, low-temperature hydrothermal systems far from the ridge axis have been investigated. These findings enable us to obtain a new view of seafloor hydrothermal systems. This paper summarizes recent observational and modeling studies on low-temperature and high-temperature hydrothermal systems. First, we briefly plot seafloor hydrothermal systems and present some historical remarks. Then, we review the most important properties of the crustal structure such as the distribution of heat sources and permeability, which control hydrothermal circulation. These are described in terms of spreading rate. For instance, a hydrothermal system on a fast-spreading ridge is hosted by a quasi-steady magma chamber under the axis, and a system on an ultraslow-spreading ridges is hosted by long-lived tectonic faults at the axis. We also introduce recent numerical simulations both for low-temperature and high-temperature systems including the authors' studies. The main topic of current research is the pattern of circulation of both systems. High-temperature systems are controlled by the phase separation of seawater and the spatial heterogeneities of heat sources. Low-temperature systems instead are mainly affected by the local permeability structure instead. The presence of seamounts is thought to account for heat transport in the oceanic crust.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124518492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"2006年ジョグジャカルタ地震は Sidoarjo 泥火山の噴出を誘発したか","authors":"J. Mori, 加納 靖之","doi":"10.5026/JGEOGRAPHY.118.492","DOIUrl":"https://doi.org/10.5026/JGEOGRAPHY.118.492","url":null,"abstract":"We examine the possible effect of shaking from the May 26, 2006 Yogyakarta earthquake (MW6.3) on the triggering of the Sidoarjo, Indonesia mud volcano, which is located about 250 km from the earthquake. The mud volcano has been erupting since May 2006. There seems to be indications from the timing of pressure changes in the neighborhood of the mud volcano and the earthquake occurrence, that the seismic waves may have affected the local fluid conditions. The level of stress changes from the earthquake waves is inferred from data of other similar sized earthquakes. The stress changes are quite small (0.005 to 0.010 MPa), but in the range of values that have triggered small earthquakes in other regions. There appeared to be pressure changes in the well drilling several minutes after the earthquake, suggesting a fluid response to the earthquake shaking. Although it seems possible that the 2006 Yogyakarta earthquake triggered small fluid pressure changes at the mud volcano, it is difficult to evaluate if there is any direct relation to the initiation of the mud eruption.","PeriodicalId":356213,"journal":{"name":"Chigaku Zasshi (jounal of Geography)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114504641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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